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    User name A. Deur

    Log entry time 03:46:18 on July26,2003

    Entry number 106932

    keyword=Elastic cross section at 2.1 GeV, 6 degree

    Here the result of the analysis on the elastic cross section at 2.1 GeV, 6 degree. The runs are from the He3 pol cell except for runs 2435, 2437 and 2439 that are from the ref cell at different He3 pressures. The run 2464 was at 10 uA. All the others were done at about 2 uA

    The blue squares are the simulation from a monte carlo using John LeRose transfer functions (these are quite old a will get improved greatly with the septum experimental data). The difference from expected He3 pol cell and expected ref cell cross sections comes from the different thickness of the cell walls (radiative corrections).
    The red triangles are a analysis with espace but the old database (not optimized). The analysis includes corrections for deadtime, temperature/density effect, N2 contamination (2% for He3 pol cell and none for ref cell runs), Glass contamination (0.7% for pol He3 cell runs and 1 to 2% for ref cell runs), VDC multitrack inefficiency (2 to 8%). Detector inefficiency is very small. Lifetime is about 99%.
    The pink triangles are from a scaler analysis, corrected from N2 and glass contamination (from 5% to 12%). The quasi-elastic contamination has been estimated to contribute to 10%. This has been done with the Monte Carlo to disentangle the elastic tail from the quasi-elastic. I account for the fact that for the scaler analysis the acceptance is much bigger without cut in order to compare the pink triangles to both the blue circles and red triangles.

    The difference between the espace analysis and the expectation is about 19%, which is satisfactory given the fact that we use crude transfer functions and data-base. Jian-Ping suggested that the worst agreement for run 2464 may come from the offset in the bcm (not accounted for in the analysis). The scalers agree within 3% to expectation which is accidental since we believe that the accuracy of the analysis to be at the level of 10 to 20%.

    Overall, this analysis shows that we don't see problems with data to extract absolute quantities.

    FIGURE 1